Dust detection by the wave instrument on STEREO: nanoparticles picked up by the solar wind?

The STEREO/WAVES instrument has detected a very large number of intense voltage pulses. We suggest that these events are produced by impact ionisation of nanoparticles striking the spacecraft at a velocity of the order of magnitude of the solar wind speed. Nanoparticles, which are half-way between micron-sized dust and atomic ions, have such a large charge-to-mass ratio that the electric field induced by the solar wind magnetic field accelerates them very efficiently. Since the voltage produced by dust impacts increases very fast with speed, such nanoparticles produce signals as high as do much larger grains of smaller speeds. The flux of 10-nm radius grains inferred in this way is compatible with the interplanetary dust flux model. The present results may represent the first detection of fast nanoparticles in interplanetary space near Earth orbit.Comment: In press in Solar Physics, 13 pages, 5 figure

Developing a Global Healthcare Innovation Index

Our understanding of medicine is being revolutionised by the pace of science. But not all the potential innovations in life sciences and medical technology are taken up into everyday practice in healthcare, even when they are shown to be beneficial. For the poorest people in the world, many innovations are not accessible because they are either unaffordable or unsuitable for their health systems. Tackling this gap requires the development of appropriate and affordable health technologies and novel business models. In the more advanced health systems there is a disconnection between the effort on research and development (R&D) and how much of this makes it into mainstream healthcare practice. Even the most evidence-based and affordable innovations can fail or are only taken up patchily, whether we compare across countries, or between localities or health organisations within countries. And technological innovation can be a problem for those responsible for paying for health systems. New technologies often increase costs because they allow us to treat more people for a longer part of their lives. Yet the general view amongst politicians, managers and others involved in healthcare is that health systems across the world need new thinking. They are increasingly facing escalating demand from an ageing population and the growing incidence of chronic disease. Healthcare is consuming an ever-increasing share of gross domestic product (GDP). The search is on for ways of providing the best quality healthcare as affordably as possible. The health technology industries – pharmaceutical and biotechnology, medical devices, information technology and the built environment (design, engineering and construction) – drive much of the innovation that takes place in healthcare. They are very big business. Collectively these companies have global revenues in the order of USD 2 trillion a year, about a quarter of overall global spending on healthcare. But they too are experiencing a changing landscape – an evolving market for their products, a changing balance of power across health systems as governments and payers seek to control costs, hence pressure on their business models. Innovation is regarded by economists and politicians as one of the main drivers of economic growth. It helps to explain why some companies, regions and countries perform better than others in terms of higher productivity and income. For companies involved in the health technology sector, and governments in countries where they are located, there is concern to ensure that their business models are sustainable and continue to successfully deliver new products to the market

Near-IR bright galaxies at z~2. Entering the spheroid formation epoch ?

Spectroscopic redshifts have been measured for 9 K-band luminous galaxies at 1.7 < z < 2.3, selected with Ks < 20 in the "K20 survey" region of the Great Observatories Origins Deep Survey area. Star formation rates (SFRs) of ~100-500 Msun/yr are derived when dust extinction is taken into account. The fitting of their multi-color spectral energy distributions indicates stellar masses M ~ 10^11 Msun for most of the galaxies. Their rest-frame UV morphology is highly irregular, suggesting that merging-driven starbursts are going on in these galaxies. Morphologies tend to be more compact in the near-IR, a hint for the possible presence of older stellar populations. Such galaxies are strongly clustered, with 7 out of 9 belonging to redshift spikes, which indicates a correlation length r_0 ~ 9-17 h^-1 Mpc (1 sigma range). Current semianalytical models of galaxy formation appear to underpredict by a large factor (about 30) the number density of such a population of massive and powerful starburst galaxies at z ~ 2. The high masses and SFRs together with the strong clustering suggest that at z ~ 2 we may have started to explore the major formation epoch of massive early-type galaxies.Comment: accepted on June 17. To appear on ApJ Letter

Polarization and kinematics in Cygnus A

From optical spectropolarimetry of Cygnus A we conclude that the scattering medium in the ionization cones in Cygnus A is moving outward at a speed of 170+-34 km/s, and that the required momentum can be supplied by the radiation pressure of an average quasar. Such a process could produce a structure resembling the observed ionization cones, which are thought to result from shadowing by a circumnuclear dust torus. We detect a polarized red wing in the [O III] emission lines arising from the central kiloparsec of Cygnus A. This wing is consistent with line emission created close to the boundary of the broad-line region.Comment: 5 pages, accepted for publication in MNRAS letter

Spacecraft charging and ion wake formation in the near-Sun environment

A three-dimensional (3-D), self-consistent code is employed to solve for the static potential structure surrounding a spacecraft in a high photoelectron environment. The numerical solutions show that, under certain conditions, a spacecraft can take on a negative potential in spite of strong photoelectron currents. The negative potential is due to an electrostatic barrier near the surface of the spacecraft that can reflect a large fraction of the photoelectron flux back to the spacecraft. This electrostatic barrier forms if (1) the photoelectron density at the surface of the spacecraft greatly exceeds the ambient plasma density, (2) the spacecraft size is significantly larger than local Debye length of the photoelectrons, and (3) the thermal electron energy is much larger than the characteristic energy of the escaping photoelectrons. All of these conditions are present near the Sun. The numerical solutions also show that the spacecraft's negative potential can be amplified by an ion wake. The negative potential of the ion wake prevents secondary electrons from escaping the part of spacecraft in contact with the wake. These findings may be important for future spacecraft missions that go nearer to the Sun, such as Solar Orbiter and Solar Probe Plus.Comment: 25 pages, 7 figures, accepted for publication in Physics of Plasma

Non-Equilibrium Processes in the Solar Corona, Transition Region, Flares, and Solar Wind \textit{(Invited Review)}

We review the presence and signatures of the non-equilibrium processes, both non-Maxwellian distributions and non-equilibrium ionization, in the solar transition region, corona, solar wind, and flares. Basic properties of the non-Maxwellian distributions are described together with their influence on the heat flux as well as on the rates of individual collisional processes and the resulting optically thin synthetic spectra. Constraints on the presence of high-energy electrons from observations are reviewed, including positive detection of non-Maxwellian distributions in the solar corona, transition region, flares, and wind. Occurrence of non-equilibrium ionization is reviewed as well, especially in connection to hydrodynamic and generalized collisional-radiative modelling. Predicted spectroscopic signatures of non-equilibrium ionization depending on the assumed plasma conditions are summarized. Finally, we discuss the future remote-sensing instrumentation that can be used for detection of these non-equilibrium phenomena in various spectral ranges.Comment: Solar Physics, accepte